/* ctr_mode.c - TinyCrypt CTR mode implementation */

/*
 *  Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *    - Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *
 *    - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 *    - Neither the name of Intel Corporation nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

#include "ctr_mode.h"
#include "constants.h"
#include "utils.h"

int tc_ctr_mode(uint8_t *out, unsigned int outlen, const uint8_t *in,
                unsigned int inlen, uint8_t *ctr, const TCAesKeySched_t sched) {
  uint8_t buffer[TC_AES_BLOCK_SIZE];
  uint8_t nonce[TC_AES_BLOCK_SIZE];
  unsigned int block_num;
  unsigned int i;

  /* input sanity check: */
  if (out == (uint8_t *)0 || in == (uint8_t *)0 || ctr == (uint8_t *)0 ||
      sched == (TCAesKeySched_t)0 || inlen == 0 || outlen == 0 ||
      outlen != inlen) {
    return TC_CRYPTO_FAIL;
  }

  /* copy the ctr to the nonce */
  (void)_copy(nonce, sizeof(nonce), ctr, sizeof(nonce));

  /* select the last 4 bytes of the nonce to be incremented */
  block_num =
      (nonce[12] << 24) | (nonce[13] << 16) | (nonce[14] << 8) | (nonce[15]);
  for (i = 0; i < inlen; ++i) {
    if ((i % (TC_AES_BLOCK_SIZE)) == 0) {
      /* encrypt data using the current nonce */
      if (tc_aes_encrypt(buffer, nonce, sched)) {
        block_num++;
        nonce[12] = (uint8_t)(block_num >> 24);
        nonce[13] = (uint8_t)(block_num >> 16);
        nonce[14] = (uint8_t)(block_num >> 8);
        nonce[15] = (uint8_t)(block_num);
      } else {
        return TC_CRYPTO_FAIL;
      }
    }
    /* update the output */
    *out++ = buffer[i % (TC_AES_BLOCK_SIZE)] ^ *in++;
  }

  /* update the counter */
  ctr[12] = nonce[12];
  ctr[13] = nonce[13];
  ctr[14] = nonce[14];
  ctr[15] = nonce[15];

  return TC_CRYPTO_SUCCESS;
}
